Threaded fasteners for direct screwing into components

Abstract

The present invention relates to a threaded fastener (10) for direct engagement with a part made of, inter alia, a light metal material, the threaded fastener (10) comprising a head and a shank having threads (20) formed thereon, the threads (20) having an outer thread radius (R A ) decreases from the cylindrical load-bearing region (TB) through the tip region (SB) to the tip (12), and the thread (20) has an outer thread radius (R A ) decreases toward the tip of the threaded fastener (12), the threaded fastener has at least five circumferentially defined ridges (14.X, 16.X), the ridges (14.X, 16.X) extending radially and having an outer radius (R) that varies in the region of the ridges (14.X, 16.X). A ) the thread (20) extends over the ridge outer radius of the ridge Emax ), where at least two of the ridges are calibration ridges (16.X) and the maximum ridge radius (R Emax ) are of equal magnitude and have a constant outer thread radius (R A ) is the load-bearing area radius (R T ) and at least three preformed ridges (14.X) are provided between the calibration ridge (16.X) and the forward-most tip (12), and each preformed ridge has a maximum ridge radius (R Emax ) is the maximum radius (R Emax ) and the maximum radius (R Emax ) decreases towards the tip (12).

Description

[Technical Field]

[0001] The present invention relates to a threaded fastener for direct screwing onto a part, and more particularly to a threaded fastener for direct screwing onto a part made of a light metal material. [Background technology]

[0002] EP 1053405 discloses a tapping screw fastener having a retaining area and a cut-out area that displaces the base material to form threads. The head-side end of the cut-out area cuts only slightly into the base material to form a calibration area for calibrating the threads cut into the base material. The lowest point between the calibration ridges in this area has the same thread radius as the cylindrical load-bearing area. These calibration ridges form two opposing fulcrums equally spaced from the centerline of the screw fastener. They must extend slightly beyond the load-bearing diameter.

[0003] A similar arrangement is disclosed in WO 95 / 14863, which teaches a self-tapping fastener having forming elements disposed on the threads to reduce the threading torque, which typically increases with increasing threading depth as the threads are formed in the substrate.

[0004] The fastener has a front region with a forming area that extends radially from the reference threads, the reference threads extending substantially from the shank to the tip, and a circumferentially limited and relatively short reference thread. The fastener has a calibration ridge in the load-bearing region that extends only slightly beyond the load-bearing threads, typically by less than 0.08 mm.

[0005] The above-mentioned threaded fasteners reduce friction during tapping (thread cutting) and achieve good fastening performance. Reliably manufacturing such calibration ridges, especially by a rolling process, is difficult because the material required to form the calibration ridges is not sufficiently available for the rolling process. Therefore, the correct formation of the calibration ridges cannot be reliably guaranteed. Summary of the Invention

[0006] An object of the present invention is to further improve the fastening performance of threaded fasteners while maintaining a small tapping torque, and to make the manufacture of threaded fasteners easier.

[0007] The above problem is solved by the characterizing part of claim 1 in combination with the preamble configuration of said claim.

[0008] A threaded fastener for direct engagement with a component, particularly a component made of a light metal material, obviously comprises a head with a drive portion and a shank with threads, the outer thread radius of which decreases from a cylindrical load-bearing region through a tip region toward the tip of the fastener, such that the outer thread radius at the end opposite the head is smaller than the outer thread radius of the load-bearing region, the tip region beginning at the point of the fastener closest to the load-bearing region where the outer thread radius is smaller than the radius of the load-bearing region, and extending to the tip of the fastener.

[0009] The threads in the tip region form internal threads in the base material of the component, and the threads in the load-bearing region are threadedly engaged with the internal threads.

[0010] In the tip region, the threads have at least five radially extending ridges, which are circumferentially limited, meaning that there are local minima between the ridges.

[0011] In some regions, the outer thread radius follows a nominal thread profile along the helix. The nominal thread profile is interpolated across the tip region using local minima between the ridges. In the region where the thread coincides with the interpolated section of the nominal thread, the thread is referred to as a "base thread," which has a base thread outer radius that increases from the tip of the threaded component toward the radius of the load-bearing region.

[0012] As before, the base thread extends in the same manner as if no ridges were provided, and the base thread outer radius preferably decreases strictly monotonically, in particular linearly, over the tip region and coincides with the load-bearing region radius in the load-bearing region.

[0013] The outer radius of the base thread in the load-bearing region is determined by the outer diameter of the cylindrical envelope in the load-bearing region. The radius of the load-bearing region is constant throughout the region where the pre-tapped threads are engaged by the raised tip region threads. Therefore, the present invention eliminates raised regions on the cylindrical portion of the external thread, as such raised regions can adversely affect the behavior of the threaded fastener in the region.

[0014] The outer thread radius in the tip region of the thread varies in the region of the ridge compared to the base thread outer radius, and the outer thread radius is correspondingly greater than the base thread outer radius. Each ridge has a maximum outer thread radius along the helix in the circumferential direction, which corresponds to a ridge maximum value corresponding to a ridge. This ensures that the outer thread radius increases or decreases along the helix throughout the ridge.

[0015] In the present invention, at least two of the protrusions are calibration protrusions, and the maximum radius of each of the calibration protrusions is the same and is greater than the radius of the load-bearing region. The maximum radius of the calibration protrusions is the calibration radius.

[0016] With at least two such calibration ridges, only the calibration ridge closest to the tip of the fastener initially provides tapping action, so that at least one calibration ridge further from the tip of the fastener does not provide tapping action or the tapping action provided by the calibration ridge further away from the tip of the fastener is significantly reduced until the calibration ridge closer to the tip of the fastener is worn away. The next calibration ridge in the direction of the load-bearing region then takes over the tapping function to the extent of the wear of the calibration ridge closer to the tip of the fastener. In this way, the load-bearing threads can engage the preformed threads of the fastener as precisely as possible and over a longer threading path, with a corresponding improvement in tapping performance. This reduces the threading torque.

[0017] Furthermore, with the fastener of the present invention, the threading torque is kept small and within narrow limits because the calibration ridges only provide additional tapping performance after the calibration ridges closer to the tip of the fastener have worn away.

[0018] By arranging the calibration ridges in the region of the decreasing base thread outer radius, the difference from the base thread outer radius is greater than the difference from the load-bearing zone radius. In this way, the material required to form the calibration ridges is available, and the calibration ridges can be more reliably produced even if the difference between the calibration radius, the maximum ridge radius of the calibration ridges, and the load-bearing zone radius is very small. The maximum ridge radius of the calibration ridges, i.e., the difference between the calibration radius and the load-bearing zone radius, is preferably very small, in particular less than 0.1 mm.

[0019] Preferably, there can be at least three calibration ridges with equal maximum ridge radii. This results in one calibration ridge closest to the tip of the fastener that still provides lower tapping performance, and two additional calibration ridges further away from the tip of the fastener. After the calibration ridge closest to the tip of the fastener wears away, the more distant calibration ridges can be used to more precisely form threads in the component. All of the above configurations are more advantageous for harder component materials, and therefore harder substrates.

[0020] Furthermore, at least three preformed ridges are provided between the calibration ridge and the forward-most fastener tip, and each preformed ridge has a maximum radius smaller than the maximum radius of the calibration ridge, i.e., the maximum radius of the calibration radius. Furthermore, each preformed ridge has a maximum radius that decreases toward the fastener tip. This configuration allows for progressive shaping of the substrate. The difference between the maximum radii of each of the plurality of consecutive ridges is preferably set so that each preformed ridge provides approximately the same tapping action.

[0021] In a preferred embodiment of the invention, the base thread outer radius increases from the tip of the threaded component through the tip region in the same manner as the maximum radius of the pre-formed ridge, and in particular, the interpolated progression of the maximum ridge radius is parallel to the interpolated progression of the local minimum.

[0022] Preferably, a local minimum of the thread outer radius exists between the load-bearing zone radius and the first ridge in the direction of the tip of the threaded fastener, and the local minimum of the thread outer radius is smaller than the load-bearing zone radius. In other words, the ridge drops to the height of the base thread before the load-bearing zone in the direction of the head, and the thread outer radius is smaller than the load-bearing zone radius. That is, the first ridge in the direction from the load-bearing zone to the tip of the threaded fastener is located entirely within the tip zone.

[0023] The ratio of the outer thread radius at the first local minimum to the load-bearing region radius is preferably less than 0.996, so that the difference in outer thread radii is large enough to allow sufficient material to be available to form the ridges.

[0024] In one advantageous embodiment of the invention, the thread has a ratio of the extrusion of the calibration radius to the load-bearing region radius to the extrusion of the calibration radius to its minimum average value that is greater than 1.4.

[0025] The minimum average thread radius is the average of a first local minimum outer thread radius and a second local minimum outer thread radius, the first local minimum being located between the load-bearing region and a first ridge closest to the load-bearing region in the direction of the tip, and the second local minimum being located between the first ridge and the ridge closest to the tip.

[0026] The increase in the maximum ridge radius profile in the direction of the head can also be degressive instead of linear, which allows for further adjustment to the tapping behavior and the hardness of the part material.

[0027] The local minimum between the ridges can coincide with the base thread outer radius and can decrease continuously, in particular linearly, over the tapping region in the direction toward the tip of the threaded fastener, at least partially extending over the tip region.

[0028] When the local minimum of the thread outer radius between the ridges coincides with the base thread outer radius, this allows the threads in the thread forming tip region to also contribute to the pull-out strength, making the threaded fastener easier to manufacture and improving the threaded fastener pull-out force.

[0029] The threads are defined radially by crests, which extend along the helix of the thread as is customary, and the point at which the outer thread radius is measured varies in a vertical plane (profile) at an angle which is called the "circumferential angle".

[0030] Thus, the circumferential angle is the angle formed by the outer radius of the thread, which is perpendicular to the axis of the threaded component on the helix, with a starting perpendicular line defined at the free end of the threaded component, in particular at the start of the thread, and the circumferential angle increases by 360° with each revolution from the starting perpendicular line at the start of the thread.

[0031] In one preferred embodiment of the ridge, the thread outer radius at a first circumferential angle position of the ridge circumferential angle can coincide with the base thread outer radius. As the circumferential angle then increases further, the thread outer radius at the circumferential angle position where the ridge reaches its maximum value coincides with the ridge maximum radius. As the circumferential angle continues to increase, the thread outer radius at the circumferential angle position where the ridge terminates coincides with the base thread outer radius. This results in the thread outer radius increasing or decreasing relative to the base thread outer radius. In this way, an improvement in load-bearing capacity can already be achieved in the region where the base thread outer radius is still increasing.

[0032] In another preferred embodiment of the ridge, the thread outer radius increases monotonically from the base thread outer radius through the ridge circumferential angle and then decreases monotonically again to the base thread outer radius, which facilitates manufacturing and provides defined tapping characteristics of the ridge. In particular, the increase and decrease follows a parabola with an apex at the maximum ridge radius.

[0033] Preferably, between two of the ridges extending parabolically along the helical line, the outside radius of the base thread increases linearly in the direction of the head.

[0034] In another advantageous embodiment of the invention, the maximum ridge radius of one pre-formed ridge is greater than the outer thread radius of the nearest ridge at the start of the nearest ridge in the direction of the head of the fastener. At the start of one of the ridges, the progression of the increase in the outer thread radius can have a slope greater than the slope of the progression of the base thread. This arrangement of ridges can ensure that all pre-formed ridges provide a tapping action only in some areas, thereby reducing tapping torque and ridge wear.

[0035] In another advantageous embodiment of the invention, the ridge circumferential angle in a plane perpendicular to the centerline of the fastener between two adjacent ridge maximum radii is equal to the circumferential angular distance α, where 360° / n-10°<α<360° / n+10°, where n is selected from 2, 3, or 4, and the angular distance of one ridge is less than 210° / n. This configuration results in a relatively short ridge circumferential angle, which reduces wear in the region of the ridge maximum radii, thereby reducing the torque of the fastener.

[0036] The ridges can extend outward in the direction of the outer radius, and can have a dimension in the longitudinal direction of the fastener that is greater than the dimension of the base threads in the longitudinal direction of the fastener.

[0037] This arrangement allows the width of the internal thread to be progressively increased at this stage by the pre-formed ridges.

[0038] In particular, the length of the thread in the tip region is less than five turns, which maximizes the portion of the threaded fastener's length that can contribute to its load-bearing function, especially when the fastener is being threaded into a blind hole.

[0039] In one advantageous embodiment of the invention, the core diameter increases from the tip to the tip region until it matches the core diameter in the load-bearing region, thereby improving the manufacturability of the threaded fastener of the invention.

[0040] The relative increase in core diameter can be less than the increase in base thread radius.

[0041] Preferably, the inclination of the thread is about 5° to 7°, which corresponds to a 3% to 5% increase in the base thread outer radius per turn. Such a gradual increase allows for the gradual formation of an internal thread in the base material, in particular due to a proportional increase in the maximum ridge radius.

[0042] In another advantageous embodiment, the thread flank width in the axial direction is narrow. The thread has a guide flank at the tip side of the threaded fastener and a pressure flank at the head side of the threaded fastener, and a reference flank angle is formed between the guide flank and the pressure flank. The reference flank angle is preferably 25° to 45°. This configuration improves the threading behavior, especially in high-strength light metal materials.

[0043] More preferably, the cross section of the raised portion of the thread at the tip of the threaded fastener is set so that the shape at the crest of the thread is elliptical.

[0044] In a particularly preferred embodiment of the invention, the guide flank and the pressure flank are connected in the region of the ridge via a thread crest, the cross-sectional profile of which is elliptical, the first eccentricity ε of which is between 0.5 and 1.

[0045] The elliptical shape of the thread crest in the region of the ridges provides a robust geometric structure at the outermost thread crest, thereby providing excellent tapping characteristics. Furthermore, the material displaced becomes less and less tolerant as the distance from the apex increases, from the outermost thread crest toward the thread root and down to the flank. This reduces the radial force required to cut the substrate, thereby making it easier for the threads to penetrate into the substrate. This also reduces wear on the ridges, which in turn improves the precision of the thread formation in the substrate, particularly of the calibrated ridges.

[0046] In addition to the elliptical shape of the crest of the ridge, the crest of the base thread in the load-bearing region can also be elliptical. This configuration of the base thread in the load-bearing region improves the contact between the base thread and the formed internal thread. In a particularly preferred embodiment of the invention, the thread is configured such that two tangents to the crest ellipse intersect to form an intersection angle or reference flank angle of less than 60°, in particular an intersection angle or reference flank angle of less than 45°.

[0047] The two tangents are each located at a point of contact on an ellipse, at the transition from the elliptical region at the crest of the thread to the elliptical regions adjacent to the thread flanks, i.e., the pressure flank and the pilot flank, and each tangent forms a half flank angle with the larger semi-major axis.

[0048] The distance from the semi-major axis to the two tangent points is greater than (1 / 3) × tan(half flank angle) × thread height, which is the difference between the base thread outer radius and half the core diameter. This configuration allows for relatively narrow thread flanks.

[0049] It is also preferred that the crests in the region of the ridges have connecting lines from the respective contact points to the apex of the semi-major axis of the thread crest, forming an apex angle with the semi-major axis of the thread crest of less than 55°, which ensures a correspondingly slim transition of the thread crest and improves the cutting behavior into the substrate.

[0050] In this way, a tangent point on the pressure flank and a tangent point on the guide flank are obtained. Lines perpendicular to the tangent lines passing through the tangent points intersect the semi-major axis at intersections. The thread crest can be preferably configured such that the distance between the tangent point and the intersection point is smaller than the distance between the intersection point and the apex of the thread crest. Preferably, the distance between the tangent point and the intersection point is less than 90% of the distance from the apex of the thread crest to the intersection point.

[0051] In a particularly preferred embodiment of the invention, the transition from the elliptical thread crest to the thread flank is tangential, which provides a smooth transition and allows the material displaced by the thread crest to continue to flow along the thread flank with low friction, thereby reducing the tapping torque.

[0052] Preferably, the ellipse may merge into a straight section of the guide flank and / or the pressure flank, the straight section being congruent to the tangent line.

[0053] In another embodiment of the invention, the guide flank and / or the pressure flank may be shaped along an elliptical path that is curved in the opposite direction to the elliptical curvature of the thread crest, and this curvature may connect directly to the thread crest or directly to a straight section of the guide flank and / or the pressure flank.

[0054] Preferably, the eccentricity of the elliptical path of the guide flank and / or the pressure flank is less than the eccentricity of the elliptical path of the thread crest, which allows the thread to widen significantly in the direction of the thread root, thereby improving the shear strength and stability of the thread.

[0055] In another advantageous embodiment of the invention, the semimajor axis of the ellipse described by the thread crest is inclined at an angle of up to 10° towards the pilot flank relative to a plane perpendicular to the center line of the threaded component.

[0056] In particular, the distance between adjacent thread flanks at 90% of the thread height is greater than 0.7 times the pitch. Furthermore, the flank width at 90% of the thread height can be less than 0.5 times the thread height. This configuration allows for a sufficiently small crest width.

[0057] The threaded fasteners are preferably made of steel.

[0058] Other advantages, features and possible applications of the invention will become apparent on reading the following description which refers to embodiments illustrated in the drawings. [Brief explanation of the drawings]

[0059] [Figure 1] FIG. 1 is a side view of a threaded fastener showing the load-bearing region and tip region. [Figure 2] FIG. 2a is a perspective view of the tip, and FIG. 2b is a plan view of the tip. [Figure 3a] FIG. 1 shows thread lines and (interpolated) core diameter. [Figure 3b] FIG. 3b is an enlarged view of a portion of FIG. 3a. [Figure 4] FIG. [Figure 5] FIG. 1 is a cross-sectional view showing the profile of a load-bearing thread. [Figure 6] FIG. 10 is a cross-sectional view showing the thread profile of the calibration ridge. DETAILED DESCRIPTION OF THE INVENTION

[0060] 1 is a side view of a threaded fastener 10 of the present invention for threading into a fastener made from a light metal material. The fastener 10 has a leading end and a head 18 at the other end of the fastener 10, the leading end being referred to as the "fastener tip 12." The fastener has threads 20 with a load-bearing region TB, in which the threads 20 have a constant outer thread radius R throughout the length of the helix. A The load-bearing region radius R is T The radius of the load-bearing region R is equal to half the outer diameter of the load-bearing region TB. T is preferably specified by the nominal outer diameter of the threaded fastener. T corresponds to half of the nominal outer diameter. The load-bearing region TB is followed by a tip region SB in the direction of the threaded component tip 12, and the thread outer radius R of the thread 20 extends over the tip region SB. A The thread diameter varies along the helix and decreases to the tip 12 of the threaded component. In the tip region SB, the threads 20 have circumferentially defined and radially extending ridges 14.2, 14.5, 14.8, 16.1, and 16.2 (also referred to as "14.X" and "16.X"). In the region of ridges 14.X and 16.X, the threads 20 have a varying outer thread radius R A The outer radius of the thread R A basically increases, and the base thread outer radius R AB The base thread 20 has an outer radius R AB The thread also increases linearly with the outer radius of the ridge R AE is the base thread outer radius R AB It also has larger ridges 14.X and 16.X.

[0061] At least two of the raised portions 14.X and 16.X in the tip region SB have the same maximum raised radius R E9max ,R E10max and the maximum radius of this protuberance RE9max ,R E10max is the radius of the load-bearing area R T Larger calibration radius R K . Such ridges are referred to as "calibration ridges" 16.X, since at least those ridges 16.X located further along the helix in the head direction ensure less reshaping to form the base threads, and instead reduce any inaccuracies in the preformed threads, especially in the crest region. The purpose is, inter alia, to reduce any inaccuracies mentioned above due to wear of the calibration ridges 16.X closer to the tip 12 of the threaded component. In particular, the friction of the threads 20 in the load-bearing region TB, which subsequently engage the tapped threads, is reduced, and the threading torque can be kept low and within narrow limits.

[0062] Between the calibration ridge 16.X and the forward-most tip 12, there are at least three pre-formed ridges 14.X for tapping, each of which has a maximum ridge radius R E1max ,R E8max is the calibration radius R K In this embodiment, eight preformed ridges 14.X are provided. The maximum ridge radius R is measured through the tip region SB in the direction of the load bearing region TB. E1max R E8max That is, the outer radius R of the thread of the local maximum value of the ridge 14.X A When the maximum ridge radius R is increased to , the depth of the base material increases and the internal thread is formed. E1max The increase in σ can be particularly clearly seen in Figure 3a, where the σ for each maximum ridge radius (here R E1max ~R E9max ) is shown, which includes an interpolated progression interval R AEMax is attached.

[0063] Figure 2a is a perspective view of the fastener tip 12 of fastener 10. As with the embodiment of Figure 1, threads 20 extend along a helix from fastener tip 12 in the head direction.

[0064] The starting point S on the thread 20, e.g., the starting point of the thread 20, is the angular position WP at which the maximum radius of the second preformed ridge 14.2 is located. E2max The thread radius angle forms a circumferential angle U with the radius at the starting point when projected onto a plane perpendicular to the threaded component centerline MA. The increment of circumferential angle U per revolution is 360°, and as the circumferential angle U increases along the threaded component centerline toward the head, the position of the outer thread radius shifts at each angular position. A plan view of the perpendicular plane is shown in Figure 2b.

[0065] The circumferential angular distance α between the maximum values of two adjacent ridges, e.g., the angular position WP E2max and WP E3max In this example, the circumferential angular distance α between the maximum values of the adjacent raised portions 14.X, 16.X is 120°, which eliminates the circumferential offset between the raised portions located axially above each other. Alternatively, the circumferential angular distance α between the maximum values of the adjacent raised portions 14.X, 16.X may be, for example, 125°, so that the raised portions are offset in the rotational direction.

[0066] Furthermore, each ridge extends over a circumferential angular distance β. Thus, each ridge 14.X, 16.X has an angular position WP at which the ridge 14.X, 16.X begins and another angular position WP at which the ridge ends. For example, the third ridge 14.3 has an angular position WP E3start Starting from the angle position WP E3end Extending to the end of the third ridge 14.3, which terminates at

[0067] Preferably, the circumferential angular distance α between two adjacent ridges is more than twice the circumferential angular distance β of the ridges.

[0068] 3a is a schematic diagram showing an example of the progression of the thread line GL at the outermost point of the thread crest over the helical line when developed, with the circumferential angle as the horizontal axis. AA general increase in the base thread outer radius can be seen across the tip region SB. The general increase in the base thread outer radius is shown as a thin dashed line, the base thread line BL. This line shows the progression of the "base thread" as the thread 20 extends without the ridges 14.X, 16.X in a specific region.

[0069] The solid line shows the progression of the actual thread line GL along the base thread through the ridge where the outer thread radius exceeds the base thread. The local maximum of the ridge is the maximum ridge radius R AEmax In this example, R AEmax The increase in is parallel to the base thread line.

[0070] In this figure, the ridges are short in the circumferential direction and only span a short angular range of up to about π / 3 (60°). E2end and WP E3start The circumferential angular distance between is approximately π / 3 (60°).

[0071] The threads are formed in the tip region SB of the threaded fastener 10, i.e., the outer thread radius R of the base thread. A In the region where the value of the calibration ridge 16.X increases continuously, in this example, linearly, the calibration ridge 16.X has three calibration ridges 16.X.

[0072] These three calibration ridges 16.X have the same maximum ridge radius RE 10Max ,R E11max ,R E12Max and this maximum ridge radius is the calibration radius R K The calibration radius R K , and thus the maximum ridge radius RE of the calibration ridge 16.X 10Max ,R E11max ,R E12Max is the load-bearing thread radius R of the threads in the load-bearing region TB of the threaded fastener T Greater than.

[0073] The calibration ridge 16.X is located in the radius increasing region of the tip region SB, so that the base thread radius R ABand the calibration radius R K The difference between the load-bearing area TB and the calibrated ridge 16.X is greater than the load-bearing area TB. In other words, the calibrated ridge 16.X can be produced with sufficient precision and high reliability using a rolling method. This makes it possible to further reliably reduce the tapping torque when directly threading such a threaded fastener into light metal.

[0074] The circumferential dimension of the ridges is approximately equal to or preferably less than the circumferential angular distance of 60°, so that friction occurs only over a small engagement angle, thereby keeping the engagement torque low.

[0075] FIG. 3b is an enlarged view of the detail of FIG. 3a, focusing on the calibration ridge 16.X. This enlarged view of the detail shows that even for the ridge closest to the load bearing region TB, the difference in outer radius relative to the base thread BL is R K -R T It can be clearly seen that this is significantly larger than the load-bearing area TB, which is only a difference of 0.1 mm, which is preferably less than 0.1 mm in the present invention.

[0076] According to the teachings of the present invention, the above arrangement allows for the precise production of the calibration ridges 16.X, even by a rolling process, thereby achieving the most precise possible shaping of the base thread.

[0077] Between the calibration ridge 16.3 closest to the load-bearing area and the load-bearing area itself, the circumferential angular position WP E12end Outer thread radius R A is the outer radius of the thread R A (WP E12end ) is a local minimum with

[0078] Load bearing area radius R T The outer radius R of the thread of the above local minimum A (WP E12end ) is preferably less than 0.996.

[0079] Furthermore, the end point of the second calibration ridge 16.2, i.e., the circumferential angular position WPE11end The outer radius of the thread R A (WP E11end ) there exists another local minimum with

[0080] In particular, the threads are formed at a radius R of the load bearing area. T the calibration radius R K The protrusion rate of the calibration radius R for the minimum average value K The ratio of the protrusion rates is greater than 1.4.

[0081] The minimum average value is the outer thread radius R of the first local minimum. A (WP E12end ) and the outer thread radius R of the second local minimum A (WP E11end ) is the average value.

[0082] Therefore, the thread configuration satisfies the following formula: (R K / (R A (WP E12end )+R A (WP E11end )) / 2))-1) / ((R K / R T )-1)>1.4 The axial dimensions of the ridges are shown in FIG.

[0083] 4 is a schematic cross-sectional view AA of the thread 20 at the transition from the load-bearing region TB to the tip region SB. From the thread base line GG, the thread 20 has a pressure flank 52, which is the head-side thread flank in the region of the calibrated ridge, and merges into a thread crest 54 with an elliptical profile. The thread tip 54 then changes toward the tip of the threaded component and returns to a thread flank or pilot flank 56. The profile of the base thread is shown by a dashed line, which would be the cross-sectional plane in the absence of the ridge. In the load-bearing region TB, the actual progression corresponds to the progression of the base thread, which has the pressure flank 42, the thread crest 44, and the pilot flank 46.

[0084] The calibration ridge 54 is circumferentially defined and extends beyond the progression of the base thread. The calibration ridge has a maximum ridge radius R AEmax which in this example has a calibration radius R K As can be seen in FIG. 4, in deviation from the course of the base thread shown by the dashed line, the ridges also extend beyond the base thread in the axial direction, and are preferably rolled in during the rolling process.

[0085] As can be seen in Figure 3b, the angular position WPE 12max In other words, in the region where the base thread height is still increasing, the base thread and the calibrated height R K The difference between the radius of the load-bearing area TB and the radius of the load-bearing area R T This allows the protrusions 54 to be fabricated with higher reliability.

[0086] The base threads have an elliptically shaped crest 44 in the load bearing region, the crest configuration of which is shown in detail in FIG.

[0087] The crest 54 has an elliptical cross section, the construction and effect of which will be explained in more detail below with reference to FIG.

[0088] The improved wear resistance of the elliptical shape of the thread crest as described above, in combination with the configuration of the calibration area in the tip region of the present invention, allows for particularly reliable forming of the internal thread.

[0089] The elliptical profile of the thread crest in the load-bearing region is particularly suitable for adjusting to the cross-sectional shape of the ridge, thereby increasing the contact area in the fastened state, which in turn can increase the pull-out force. The shape of the ridge crest is similar to that of the base thread, and is described in more detail below with reference to Figure 6.

[0090] 5 is a cross-sectional view of the threads in the load-bearing region TB, which are provided with oval-shaped thread crests 44. This thread form is essentially provided on the base threads over the tip region SB of the threaded fastener, i.e., in the area between the ridges.

[0091] The cross-sectional profile of the thread crest 44 is an elliptical shape SE. The thread crest 44 is joined to a pilot flank 46 toward the tip of the fastener and to a pressure flank 42 toward the head of the fastener. The crest apex SP is located at the apex of the ellipse SE at the intersection of the ellipse SE with the semi-major axis HA.

[0092] The thread crest 44 transitions into the pressure flank 42 at transition point UP1 and into the pilot flank 46 at transition point UP2. Transition points UP1 and UP2 are points where the thread profile departs from the elliptical path SE of the thread crest 44.

[0093] Tangents T1 and T2 can be formed at the transition points UP1 and UP2, respectively, and these tangents T1 and T2 determine the flank angles.

[0094] The tangent T1 is located at a transition point UP1 and forms a pressure flank angle LF with the semimajor axis HA.

[0095] A perpendicular line to this tangent line passing through the transition point UP1 intersects the semi-major axis at the intersection point BP1. The thread crest is preferably configured so that the distance between the intersection point BP1 and the transition point UP1 is less than 90% of the distance between the apex SP and the intersection point BP1. This ensures sufficient curvature of the thread crest to achieve good flow of the material as it is displaced, thereby reducing wear on the thread crest during the tapping process.

[0096] More preferably, the shape of the thread crest is such that the connecting line VL1 between the transition point UP1 and the apex SP forms an apex angle VL1-HA with the semi-major axis HA, which is in particular less than 45° and in this embodiment is approximately 22°.

[0097] The thread crest 44 is configured so that the relationship that applies to UP1 also applies to UP2 on the pilot flank.

[0098] The tangent T2 is located at a transition point UP2 and forms a guide flank angle FF with the semimajor axis HA.

[0099] A line perpendicular to this tangent line T2 passing through the transition point UP2 intersects with the semi-major axis at the intersection point BP2. The thread crest is preferably configured so that the distance between the intersection point BP2 and the transition point UP2 is less than 90% of the distance between the apex SP and the intersection point BP2. This ensures sufficient curvature of the thread crest to achieve good flow of the material as it is displaced, thereby reducing wear on the thread crest during the tapping process.

[0100] More preferably, the shape of the thread crest is such that the connecting line VL1 between the transition point UP2 and the apex SP forms an apex angle VL1-HA with the semi-major axis HA, which is in particular less than 45° and in this embodiment is approximately 22°.

[0101] Furthermore, a base flank angle can be determined, which is obtained by adding the pressure side flank angle LF and the guide side flank angle FF. In this embodiment, the base flank angle is 35°.

[0102] The thread is preferably configured such that a line parallel to the tangent line T1 passing through the apex intersects with the thread base line at the base point FP1. In the present invention, the distance A1 from the base point FP1 to the semi-major axis is at most three times the distance A2 from the transition point UP1 to the semi-major axis.

[0103] In the embodiment described herein, the threads are configured such that the distance A1 is approximately twice the distance A2 from the transition point to the semi-major axis HA, which allows for a slim thread profile.

[0104] In this embodiment, at least a portion of the flank profile of both the pilot flank 46 and the pressure flank 42 is defined by an elliptical contour, with the eccentricity of the flank ellipses FE1, FE2 being significantly less than the eccentricity of the thread crest ellipse SE.

[0105] 6 is a thread cross-section of another thread configuration in the tip region SB of a threaded fastener 10, showing the crests 54 of the thread region in the region of the ridges. The elliptical crests 54 improve tapping characteristics, thereby reducing wear on the calibrated ridges formed as described above. Furthermore, the ridge profile is shown to be opposite the thread cross-section of the base thread having the crests 34, since if the base thread had a uniformly increasing transition at this point, the line of intersection through the ridged threads would be located at the cross-section.

[0106] Here, the apex SP is spaced from the centerline of the fastener by the maximum ridge radius for each ridge.

[0107] The progression on the tip ellipse is similar to the progression of the tip ellipse shown in FIG.

[0108] Because the thread profile in the load-bearing region is the same as the base thread profile, the tangent line T1 to the pressure flank is located at the transition point UP1 of the crest ellipse to the pressure flank, in the region where the ridge is parallel to the tangent line T1 to the ellipse at the transition to the pressure flank in the load-bearing region TB. Therefore, both form the same pressure flank angle with the semi-major axis HA. The same rule applies to the tangent line T2 in relation to the pilot flank.

[0109] In this respect, the cross-sectional profile of the ridge essentially corresponds to the profile of the load-bearing area. Only the area where the thread flanks follow the tangent lines T1 and T2 is longer at the ridge. As a result, a thread larger than the load-bearing area is pre-tapped, which can engage in the load-bearing area by means of a flange area parallel to the pre-tapped internal thread.

[0110] The calibration ridge closest to the load bearing area has a similar configuration, but the difference between the base threads and the ridge is greater than the difference between the threads and the ridge in the load bearing area, which ensures reliable manufacturing of the ridge while producing a slightly larger pre-formed internal thread.

Claims

1. A threaded fastener (10) for direct screwing onto a part made, in particular, of light metal material, a head and a shank provided with threads (20); The outer thread radius (R Ａ ) is the radius of the constant load-bearing area (R Ｔ ) through a tip region (SB) toward the tip (12) of the threaded component, The thread (20) has an outer thread radius (R Ａ ) decreases toward the tip of the threaded component (12), the threads (20) have at least five circumferentially defined ridges (14.X, 16.X), The maximum radius (R Ｅ１ｍａｘ ;R Ｅ２ｍａｘ , R Ｅ８ｍａｘ In the region of the protuberances (14.X, 16.X), the outer thread radius (R Ａ The ridges (14.X, 16.X) extend in the radial direction with varying radii (R ), and at least two of the ridges are calibration ridges (16.X), and each of the calibration ridges (16.X) has a maximum radii (R ). Ｅ１１ｍａｘ , R Ｅ１２ｍａｘ ) are of equal magnitude, and the load-bearing area radius (R Ｔ ) larger than the calibration radius (R Ｋ ) and at least three pre-formed ridges (14.X) are provided between said calibration ridge (16.X) and said forward-most threaded fastener tip (12); The maximum radius (R ＡＥｍａｘ ) is the maximum radius (R ＡＥｍａｘ ) and the maximum ridge radius (R ＡＥｍａｘ ) decreases in the direction of the tip (12) of the threaded part. A threaded fastener (10) characterized in that

2. The load-bearing region radius (R Ｔ ) and the first of the ridges in the direction of the threaded fastener tip (12). Ａ ) and there is a local minimum of the outer thread radius (R Ａ The local minimum of the load-bearing region radius (R Ｔ ) smaller than The threaded fastener according to claim 1.

3. The load-bearing region radius (R Ｔ ) of the first local minimum relative to the outer thread radius (R Ａ (WP Ｅ１２ｅｎｄ )) is less than 0.996; The threaded fastener according to claim 2.

4. The threads are spaced apart by the load-bearing radius (R Ｔ ) to the calibration radius (R Ｋ ) for the proportion of overflow, the minimum average value ((R Ａ (WP Ｅ１２ｅｎｄ ) + R Ａ (WP Ｅ１１ｅｎｄ )) / 2) Ｋ ) the ratio of the protrusion rate is more than 1.4, wherein said minimum average value is the outer thread radius (R ) of a first local minimum between said load bearing area and the first of said calibration ridges (16.3). Ａ (WP Ｅ１２ｅｎｄ ) and the outer thread radius (R ) of the second local minimum between the first calibration ridge (16.3) and the second calibration ridge (16.2). Ａ (WP Ｅ１１ｅｎｄ ) and the average value of The threaded fastener according to claim 2 or 3.

5. From the tip (12) through the tip region, the maximum radius (R ＡＥｍａｘ ) at the local minimum between the preformed ridges (14.X) Ａ ) increases as well as 6. A threaded fastener according to any one of claims 1 to 5.

6. The maximum radius of the raised portion (R ＡＥｍａｘ ) gradually increases from the tip (12) of the threaded component, 5. The threaded fastener according to claim 1.

7. The first circumferential angle position (WP) of the circumferential angle (U) ＥＸｓｔａｒｔ ) of the outer thread radius (R Ａ ) is the base thread outer radius (R ＡＢ ) and as it continues to increase, it reaches the maximum radius (R ＡＥｍａｘ ) and, as it increases, the corresponding circumferential angle position (WP) of the circumferential angle (U) at the end of the ridge ＥＸｅｎｄ ) at the base thread outer radius (R ＡＢ ) again matches, 7. A threaded fastener according to any one of claims 1 to 6.

8. In one of the raised portions (14.X, 16.X), the thread outer radius (R Ａ ) is the base thread outer radius (R ＡＢ ) over a circumferential angular distance (β), and then the base thread outer radius (R ＡＢ ) and then decreases until it matches again, and in particular, it follows a parabolic shape. The threaded fastener according to claim 7.

9. Between two adjacent pre-formed ridges (14.X), the base thread outer radius (R ＡＢ ) increases linearly, The threaded fastener according to claim 8.

10. The load-bearing region radius (R Ｔ ) is the calibration radius (R Ｋ ) is more than 90% of 10. A threaded fastener according to any one of claims 1 to 9.

11. The calibration radius (R Ｋ ) is the maximum radius of the load-bearing area (R Ｔ ) is 0.1 mm larger than Threaded fastener according to any one of claims 1 to 10.

12. The maximum ridge radius (R ＡＥｍａｘ ) is the thread outer radius (R ) nearest the start of the nearest ridge in the direction of the head (18). Ａ ) is greater than Threaded fastener according to any one of claims 1 to 11.

13. the circumferential angle (U) in a plane perpendicular to the centerline of the threaded component between two adjacent ridge maxima is equal to the circumferential angular distance (α), where 360° / n-10°<α<360° / n+10°, n is selected from 2, 3, or 4, and the angular distance (β) of one ridge is less than 210° / n; Threaded fastener according to any one of claims 1 to 12.

14. The protuberances (14.X, 16.X) also extend axially beyond the base thread, in particular extending axially beyond the base thread on both sides. Threaded fastener according to any one of claims 1 to 13.

15. the length of the thread (20) over the tip region (SB) is less than 5 turns; Threaded fastener according to any one of claims 1 to 14.

16. The pitch of the threads is about 5° to 7°, which corresponds to a 3% to 5% increase in the base thread outer radius per turn. Threaded fastener according to any one of claims 1 to 15.

17. The core diameter (D Ｋ ) is increasing, Threaded fastener according to any one of claims 1 to 16.

18. The core diameter (D Ｋ ) relative increase in the base thread radius (R ＡＢ ) is smaller than the increase in 18. The threaded fastener of claim 17.

19. The thread flank width is narrow in the axial direction, The threads have a pilot flank (46, 56) on the tip side (12) of the fastener and a pressure flank (42, 52) on the head side (18) of the fastener, Between the two flanks, a base flank angle of 30° is formed in particular. Threaded fastener according to any one of claims 1 to 18.

20. the guide flank (46, 56) and the pressure flank (42, 52) are connected via a thread crest (44, 54); the profile contour of the thread crest follows an elliptical path; 20. A threaded fastener according to any one of claims 1 to 19.

21. the ridges in the crest (44, 54) of the load-bearing region (TB) and / or in the tip region (SB) are configured such that a tangent (T1) at a contact point (UP1) with the ellipse at the transition with the pressure flank (42, 52) forms a pressure flank angle (LF) of less than 30°, in particular less than 25°, with the semi-major axis (HA) of the ellipse, a tangent (T2) at a contact point (UP2) with the ellipse at the transition with the guide flank (46, 56) forms a pressure flank angle (LF) with the semi-major axis (HA) of the ellipse of less than 30°, in particular a pressure flank angle (LF) of less than 25°; 21. The threaded fastener of claim 20.

22. the distance from the raceway semi-major axis (HA) to the tangent point (UP1) is greater than (1 / 3) × thread height × tan (pressure flank angle), and the distance from the raceway semi-major axis (HA) to the tangent point (UP2) is greater than (1 / 3) × thread height × tan (pilot flank angle); 22. The threaded fastener according to claim 20 or 21.

23. each connecting line (VL1; VL2) from the contact point (UP1; UP2) at the crest of the thread to the apex (SP) of the semi-major axis (HA) forms with the semi-major axis (HA) a vertex angle (VL1-HA, VL2-HA) of less than 55°, in particular a vertex angle (VL1-HA, VL2-HA) of less than 45°; 23. The threaded fastener according to claim 21 or 22.

24. the thread crest is configured such that a line perpendicular to the tangent (T1, T2) at the tangency point (UP1, UP2) intersects the semi-major axis at an intersection point (BP1; BP2), and the distance between the intersection point (BP1; BP2) and the transition point (UP1, UP2) is less than 90% of the distance between the apex (SP) and the intersection point (BP1; BP2). Threaded fastener according to any one of claims 1 to 23.

25. the transition from the elliptical thread crest (34, 44) to the thread flank (32, 36; 42, 46) is tangential; Threaded fastener according to any one of claims 21 to 24.

26. the guide flank (46, 56) and / or the pressure flank (42, 52) are shaped along an elliptical path that is curved in the opposite direction to the ellipse (SE) described by the thread crest (44, 54), 26. The threaded fastener of claim 25.

27. the eccentricity of the elliptical path of the guide flank (46, 56) and / or the pressure flank (42, 52) is less than the eccentricity of the elliptical path of the thread crest; 27. The threaded fastener of claim 26.

28. The semimajor axis (HA) of the ellipse (SE) described by the thread crest is inclined at an angle of up to 10° toward the pilot flank (46, 56) relative to a plane perpendicular to the center line of the threaded component. Threaded fastener according to any one of claims 21 to 27.

29. The distance between adjacent thread flanks at 90% of the thread height is greater than 0.7 times the pitch, and the flank width is less than 0.5 times the thread height.

30. A threaded fastener according to any one of claims 1 to 29.

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